Evaluation of bonded and bolted repair techniques with finite element method Mehmet Caliskan * Sakarya University, Vocational School, Hendek Campus, Sakarya, 54187 Turkey Received 28 June 2005; accepted 30 January 2006 Available online 27 April 2006 Abstract In this study, the efficiencies of the patch were checked under mechanical forces using an analytical method for bonded and bolted repairing methods using composite single lap joint, and also compared these analytical results with previous experimental studies. In the present analytical investigation, glue method was used for bonding and contact-target for bolted repairing. Every material was assumed to be linear isotropic. Central processor unit process time of bolted study was longer than the bonded one. The measured and predicted strain values were in agreement, verifying the accuracy of the predicted tensile loads. For lower loads, glued repairing was obtained as homogeneous load distribution, but bolted repairing as heterogeneous. As a result of this study, the bonded repair was found to be better than the bolted one for repairing of composite single lap joint. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Bonded and bolted repair; Composite patch; Aluminum 2024-T3 alloy; Finite element method; Analytic investigation; Single lap joint; Stress; Strain 1. Introduction Using of composite materials is getting increase in the manufacturing of aerospace structure due to their high strength/weight ratios. In these structures, fastened joints are indispensable for the assembly of structural compo- nents. Development of efficient methods for the design and analysis of fastened composite joints has been the focus of numerous researches over the years. Researchers first proposed to repair of cracked metal aircraft structures using adhesively bonded patches fabricated from compos- ite materials [1]. A number of analyses concerning analyti- cal, numerical and experimental analysis have been carried out to develop design systems for composite repairs of metallic aircraft structures. The advantages of adhesive bonding versus traditional joining methods, are numerous. The stress concentrations that exist near the holes of a riveted or bolted joint, are avoided when using adhesive bonding. Also, there is no dis- tortion of material properties as is often the case in a welded joint. Secondly, as different adhesive types cover a large range of material properties, adhesive joints can more easily be designed to meet specific load conditions and other requirements. One of the disadvantages of adhesive bonding is their inability to be disassembled, in case of inspection or maintenance [2]. In general composite repairs have been done on military aircrafts [3]. Recently, Textron has advanced the applica- tion of bonded repairs to civilian aircraft by fixing bonded doublers on Federal Express’ Boeing 747s for assessment [4]. Considerable researches have been performed to develop the technology of bonded composite repairs in air- craft structures. Alan Baker pioneered these researches at the aeronautical and maritime research laboratory for the Royal Australian Air force. Outlines of continuing investigation to progress the sympathetic and certainty in bonded repairs is AMRL’s work on judgment models for 0261-3069/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2006.01.024 * Tel.: +90 532 2606615. E-mail address: caliskan@sakarya.edu.tr. www.elsevier.com/locate/matdes Materials and Design 27 (2006) 811–820 Materials & Design